import java.io.*;
import java.util.*;
import java.math.*;
import java.util.*;
 
class Main {
 
	public static void main(String[] args) throws Exception {
		BufferedReader k = new BufferedReader(new InputStreamReader(System.in));
		// Scanner k = new Scanner(System.in);
 
		StringBuilder out = new StringBuilder();
		BigInteger arr[] = new BigInteger[1000];
		arr[0]=BigInteger.ZERO;
		arr[1]=BigInteger.ONE;
		BigInteger sum = BigInteger.ONE;
		for (int i = 2; i < 1000; i++) {
 
			if((i&1)==0) arr[i]=sum;
			else arr[i] = sum.add(BigInteger.ONE);
			sum = sum.add(arr[i]);
		}
		String s;
		while((s=k.readLine())!=null){
			out.append(arr[Integer.parseInt(s)].toString());
			out.append("\n");
		}
		System.out.print(out.toString());
		k.close();
	}
}
 

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